This invention relates to semiconductor devices and their fabrication and in particular to a selective etching technique.
Multilayered heteroepitaxial wafers are used in the fabrication of a large number of semiconductor components. To define the actual component it is frequently necessary to undercut selectively one or more of these layers. An example of such a component is the mass transport buried heterostructure (MTBH) laser as described, for example, by Z. L. Liau et al. Appl. Phys. Lett. 40 (7) pp 568-570, Apr. 1st, 1982; T. R. Chen et al J. Appl. Phys. 54 (5) pp 2407-2412, Mar 83; or A. Hasson et al. Appl. Phys. Lett. 43(5). pp 403-405, Sept. 1st, 1983).